THE TOWNSHEND COLLECTION. 121
strictly scientific classification of precious stones is possible.
Those in the Townshend collection have been described in the same order
as that adopted in chapter vii. It so happens that the diamond, as
consisting of the pure element carbon, takes for every reason
the first place ; while the sapphire and ruby, as varieties of
corundum, the oxide of aluminium, naturally fall into the second
position. Other species are grouped roughly in accordance with some
prominent constituent :
CarBON . Diamond.
AlumINIUM . Corundum, spinel, turquoise, topaz, tourmaline, garnet.
Magnesium . Peridot.
Glucinum . Beryl, chrysobery], phenakite, euclase.
Zirconium . Zircon.
Silicon . Opal, quartz, iolite, moonstone.
are, as might have been expected, some stones unrepresented in the
Townshend collection. Amongst these may be named—Alexandrite, Axinite,
green garnet or Demantoid, Spes-sartite, Odontolite, Phenakite,
Spodumene, and Sphene. Any one interested in precious stones should,
after inspecting the Townshend collection, turn to the general
collection of rings in the museum. The beautifully and curiously cut
diamond in a ring found at Petersham (No. 780—1904) ; the two Indian
thumb-rings of white jade (1022 and 1023—1871) ; the Persian turquoise
with gold-inlays (965—1871) ; and the two fine bloodstones, (735 and
749— 1871) are specially noticeable.